Restoring HDFS NameNode Metadata

Scenario

NameNode data needs to be recovered in the following scenarios: data is modified or deleted unexpectedly and needs to be restored. After an administrator performs critical data adjustment in NameNode, an exception occurs or the operation has not achieved the expected result. All modules are faulty and become unavailable. Data is migrated to a new cluster.

System administrators can create a recovery task in FusionInsight Manager to recover NameNode data. Only manual restoration tasks are supported.

• Data restoration can be performed only when the system version is consistent with that during data backup.
• To recover data when the service is running properly, you are advised to manually back up the latest management data before recovering data. Otherwise, the NameNode data that is generated after the data backup and before the data recovery will be lost.
• It is recommended that a data restoration task restore the metadata of only one component to prevent the data restoration of other components from being affected by stopping a service or instance. If data of multiple components is restored at the same time, data restoration may fail.

  HBase metadata cannot be restored at the same time as NameNode metadata. As a result, data restoration fails.

Impact on the System

• After the data is restored, the data generated after the data backup and before the data restoration is lost.
• After the data is recovered, the NameNode needs to be restarted and is unavailable during the restart.
• After data is restored, metadata and service data may not be matched, the HDFS enters the security mode, and the HDFS service fails to be started. .

Prerequisites

• If you need to restore data from a remote HDFS, a standby cluster has been created and the data has been backed up. For details, see Backing Up HDFS NameNode Data. If the active cluster is deployed in security mode and the active and standby clusters are not managed by the same FusionInsight Manager, mutual trust has been configured. For details, see Configuring Mutual Trust Between MRS Clusters. If the active cluster is deployed in normal mode, no mutual trust is required.

• Cross-cluster replication has been configured for the active and standby clusters. For details, see Enabling MRS Inter-Cluster Replication.
• Time is consistent between the active and standby clusters and the NTP services on the active and standby clusters use the same time source.
• On FusionInsight Manager, all the NameNode role instances whose data is to be recovered are stopped. Other HDFS role instances must keep running. After data is recovered, the NameNode role instances need to be restarted. The NameNode role instances cannot be accessed during the restart.
• The NameNode backup files are stored Data path/LocalBackup/ on the active management node.

Restoring HDFS NameNode Metadata

1. On FusionInsight Manager, click Cluster, click the name of the desired cluster, and choose Services > HDFS. On the displayed page, click Instances and click NameNode to check whether the NameNode instances of the data to be restored are stopped. If the NameNode instances are not stopped, click Stop Instance in the upper right corner.
2. On FusionInsight Manager, choose O&M > Backup and Restoration > Backup Management.
3. In the Operation column of a specified task in the task list, choose More > View History to view historical backup task execution records.

   In the displayed window, locate a specified success record and click View in the Backup Path column to view the backup path information of the task and find the following information:

   • Backup Object specifies the data source of the backup data.
   • Backup Path specifies the full path where the backup files are saved.

     Select the correct item, and manually copy the full path of backup files in Backup Path.

4. On FusionInsight Manager, choose O&M > Backup and Restoration > Restoration Management.
5. Click Create.
6. Set Task Name to the name of the restoration task.
7. Select the cluster to be operated from Recovery Object.
8. In the Restoration Configuration area, select NameNode.
9. Set Path Type of NameNode to a backup directory type.

   The settings vary according to backup directory types:

   • LocalDir: indicates that the backup files are stored on the local disk of the active management node.
     If you select LocalDir, set the following parameters:

     • Source Path: indicates the full path of the backup file on the local disk, for example, Backup path/Backup task name_Task creation time/Version_Data source_Task execution time.tar.gz.
     • Target NameService Name: indicates the NameService name of the backup directory. The default value is hacluster.
   • RemoteHDFS: indicates that the backup files are stored in the HDFS directory of the standby cluster.
     If you select RemoteHDFS, set the following parameters:

     • Source NameService Name: indicates the NameService name of the backup data cluster. You can enter the built-in NameService name of the remote cluster, for example, haclusterX, haclusterX1, haclusterX2, haclusterX3, or haclusterX4. You can also enter a configured NameService name of the remote cluster.
     • IP Mode: indicates the mode of the target IP address. The system automatically selects the IP address mode based on the cluster network type, for example, IPv4 or IPv6.
     • Source NameNode IP Address: indicates the NameNode service plane IP address of the standby cluster, supporting the active node or standby node.
     • Source Path: indicates the full path of HDFS directory for storing backup data of the standby cluster, for example, Backup path/Backup task name_Data source_Task creation time/Version_Data source_Task execution time.tar.gz.
     • Queue Name: indicates the name of the Yarn queue used for backup task execution. The name must be the same as the name of the queue that is running properly in the cluster.
     • Target NameService Name: indicates the NameService name of the backup directory. The default value is hacluster.
   • NFS: indicates that backup files are stored in the NAS using the NFS protocol. If you select NFS, set the following parameters:
     • IP Mode: indicates the mode of the target IP address. The system automatically selects the IP address mode based on the cluster network type, for example, IPv4 or IPv6.
     • Server IP Address: indicates the IP address of the NAS server.
     • Source Path: indicates the full path of the backup file on the NAS server, for example, Backup path/Backup task name_Data source_Task creation time/Version_Data source_Task execution time.tar.gz.
     • Target NameService Name: indicates the NameService name of the backup directory. The default value is hacluster.
   • CIFS: indicates that backup files are stored in the NAS using the CIFS protocol. If you select CIFS, set the following parameters:
     • IP Mode: indicates the mode of the target IP address. The system automatically selects the IP address mode based on the cluster network type, for example, IPv4 or IPv6.
     • Server IP Address: indicates the IP address of the NAS server.
     • Port: indicates the port number used to connect to the NAS server over the CIFS protocol. The default value is 445.
     • Username: indicates the username set when the CIFS protocol is configured.
     • Password: indicates the password set when the CIFS protocol is configured.
     • Source Path: indicates the full path of the backup file on the NAS server, for example, Backup path/Backup task name_Data source_Task creation time/Version_Data source_Task execution time.tar.gz.
     • Target NameService Name: indicates the NameService name of the backup directory. The default value is hacluster.
   • SFTP: indicates that backup files are stored in the server using the SFTP protocol.
     If you select SFTP, set the following parameters:

     • IP Mode: indicates the mode of the target IP address. The system automatically selects the IP address mode based on the cluster network type, for example, IPv4 or IPv6.

     • Server IP Address: indicates the IP address of the server where the backup data is stored.
     • Port: indicates the port number used to connect to the backup server over the SFTP protocol. The default value is 22.
     • Username: indicates the username for connecting to the server using the SFTP protocol.
     • Password: indicates the password for connecting to the server using the SFTP protocol.
     • Source Path: indicates the full path of the backup file on the backup server, for example, Backup path/Backup task name_Data source_Task creation time/Version_Data source_Task execution time.tar.gz.
     • Target NameService Name: indicates the NameService name of the backup directory. The default value is hacluster.
   • OBS: indicates that backup files are stored in OBS.

     If you select OBS, set the following parameters:

     • Source Path: indicates the full OBS path of a backup file, for example, Backup path/Backup task name_Data source_Task creation time/Version_Data source_Task execution time.tar.gz.
     • NameService Name: indicates the NameService name of the backup directory. The default value is hacluster.
       

       Only MRS 3.1.0 or later supports saving backup files in OBS.

10. Click OK.
11. In the restoration task list, locate a created task and click Start in the Operation column to execute the restoration task.
    • After the restoration is successful, the progress bar is in green.
    • After the restoration is successful, the restoration task cannot be executed again.
    • If the restoration task fails during the first execution, rectify the fault and click Retry to execute the task again.

12. On FusionInsight Manager, click Cluster, click the name of the desired cluster, and choose Services > HDFS. On the displayed page, click Configurations and click All Configurations.

    On the displayed page, enter the password of the administrator who has logged in for authentication and click OK. After the system displays "Operation succeeded", click Finish. The service is started successfully.